The invention relates to a light curing device, especially for a light-induced polymerization of the dental materials in the mouth of a patient, wherein the light curing device comprises a light source that is received in the hand-held portion together with a reflector for the light emitted by the light source and also comprises a cooling fan. The light source is supported in a substantially dust-tight light source casing and has provided at its exterior cooling ribs. The light source casing is of a two-part construction and has a counter cone member facing the light source.
Such a light curing device is known from German Offenlegungsschrift 29 01 534. In this known light curing device a reflector is embodied as a thin layer filter and is designed to reflect the light emitted by the light source and required for polymerization. Light of longer wave length, however, is to penetrate the reflector. The penetrating infrared radiation is then to be absorbed by a heat conducting element arranged in an air flow and is to be dissipated in this manner. In addition, cooling air flows along the holder for the reflector and thus also contributes to the cooling of the reflector. An absorption filter is provided on the light guide and is designed to absorb heat radiation present thereat.
Furthermore, it is already known to use instead of the holder a counter cone member which additionally reflects the light reflected by the reflector and thus contributes to improved light output. A light curing device with such a counter cone member, is for example, known from German Offenlegungsschrift 42 11 230.
Light curing devices employed in the dental practice must have a high light output and must provide this light output reliably within a precisely defined time interval. The dentist must be able to rely on the device in regard to complete polymerization being achieved by the dispensed amount of radiation. Otherwise, the filling would be soft and gaps could form at the edges which would result in secondary tooth decay which may result in liability suits being filed against the dentist in regard to insufficient curing and the thus caused problems.
It is therefore especially important that even after extended operation of the light curing device a sufficient light output is realized.
In order to ensure this, a certain reserve potential is employed with respect to the light output so that the operational voltage can be slightly increased when the optimum efficiency of the light source is reduced. Even though light sources of a very high light efficiency, especially in the form of halogen lamps, are available, they transform a relatively large portion of the power supplied thereto into heat energy so that without a corresponding cooling action overheating of the device is encountered.
Furthermore, from German patent 28 41 112 a light curing device is known which comprises a hood-shaped inner housing that is placed on top of the reflector of the halogen lamp provided therein. In this manner, a substantially dust-tight interior chamber is provided and the inner housing is also provided with cooling ribs.
Despite large surface area cooling ribs at the forward end of the inner housing, too much heat energy is usually observed which results in a great service life reduction or optionally also in failure of the employed constructive components, especially since the cooling air flow is selected such that the edge of the reflector is still cooled but the transition portion between the halogen lamp and the reflector is arranged so as to be relatively protected from the air flow, and cooling by the cooling air flow is thus only minimal.
In order to realize the required cooling action, it is known to provide respectively strong fans. They generate, however, undesirable exhaust air and also cause unpleasant noise. Independent of the exiting direction of the exhaust air generated by the fan, the exiting air flow is disruptive because results in air turbulence within the dental practice which, especially with regard to hygienic considerations, is undesirable.
A further undesirable aspect is that the fan after the curing device has been turned off will continue to run for a while. This necessary in conventional light curing devices in order to avoid heat build-up.
It is therefore an object of the present invention to provide a light curing device of the aforementioned kind which is able to provide over an extended period of time reliably the desired light output but at the same time provides a reduced airflow and is at the same time dimensioned such that heat build-up will be avoided.